Device for rapidly and precisely mounting flexible printing plates

ABSTRACT

Two clamping rails are mounted in a printing cylinder and at least one of these rails is slidable in directions transverse of the axis of the cylinder. For sliding this rail into proper position, an eccentric disc is suitably turned in the center of the cylinder. The motion of the disc is transmitted to the clamping rail by suitable linkage subject to intermediate spring action and subject to a force acting between the two rails, biasing them apart.

United States Patent 1191 Johne et a1. Mar. 5, 1974 [54] DEVICE FOR RAPIDLY AND PRECISELY 1,866,566 7/1932 Horton 101/410 O ING FLEXIBLE PRINTING PLATES 1,049,195 12/1912 Banzett... l01/4l5.l 3,557,695 1/1971 Preuss 101/4151 [75] Inventors: Hans Johne; Gunter Schumann;

Ammed Jehring; Kurt FOREIGN PATENTS OR APPLICATIONS Reichenberger, all of Radebeul, 951,899 3/ 1964 Great Britain 101 /4151 Germany 1,209, 21 3/1960 France 959,513 6/1964 Great Britain.. Asslgneel VEB yg p Leipzig Kombinat 425,334 8 1924 Germany fur Polygraphische Maschinen und 817,441 7/1959 Great Britain Ausrostungen, Leipzig, Germany 1,184,855 7/1968 Great Britain 101/4151 [22] Filed Apr. 1971 Primary ExaminerR0bert E. Pulfrey [21] Appl. No.: 139,067 Assistant Examiner-Eugene H. Eickholt Attorney, Agent, or Firm-A. C. Nolte, J1'.; Edward B. 521 US. Cl. 101/4151 Hume; Bruce Hmnburg [51] Int. Cl B411 29/04 [58] Field of Search 101/4151, 409, 410 ABSTRACT V Two clamping rails are mounted in a printing cylinder References Cited and at least one of these rails is slidable in directions UNITED STATES PATENTS transverse of the axis of the cylinder. For sliding this 2,820,409 1/1958 Johnson 101 4151 fail into P p Position, an eccentric disc is Suitably 3 017 30 1 9 2 penner 10 415 turned in the center of the cylinder. The motion of the 3,359,899 12/1967 Luehrsn 101/415.1 disc is transmitted to the clamping rail by suitable 3,191,532 6/1965 Hermach et a1. 101/4151 linkage subject to intermediate spring action and sub- R25,877 10/1965 NOI'IOII 101/415.l ject to a force acting between the two rails 2,737,887 3/1956 Gericke 101 4151 them apart 2,694,976 11/1954 Huck 10l/4l5.l 2,296,533 9/1942 Neal 101/4151 9 Claims, 10 Drawing Figures PATENTED 5 I974 SiEEIlBFll INVENTORS HANS JOHNE ATTORNEYS PATENTEUIMR 5191;

INVENTORS HANS JOHNE GUNTER SCHUMANN ARNFRIED JEHRING KURT REICHENBERGER FIG. 5

ATTORNEYS PAIENIEU 3,795,193

saw a nr 4 FIG. IO

INVENTORS HANS JOHNE GUNTER .SCHUMANN ARNFRIED JEHRING KURT REICHENBERGER ATTORNEYS BACKGROUND AND NATURE OF THE INVENTION Difficulties have been encountered in some of the major preparatory and auxiliary operations for the use of rotary sheet presses. As a result, the builders of such machines have given much attention to this field and have proposed a multiplicity of constructions.

According to some of the known procedures, the flexible printing plates commonly used are attached to the form cylinder by engagement between notches or holes in said plates and guide pins indexed therewith and set in clamping rails. This technique has the drawback, among others, that it requires comprehensive and reliable systems of index holes and index pins, not only in the machine but in printing plates and, correspondingly, in the art work used for preparation of these plates. These systems have been hard to provide and maintain. Moreover, unavoidable errors in guide pin tolerances, encountered incident to the printing procedures, could not be compensated. Extensive tests were needed to equalize the printing start line of the plate with the printing start line of the machine; and it was impossible to take care of irregular lengths of printing plates.

In other known devices, attempts were made to readjust the position of the flexible printing plate, on the cylinder, by means other than indexing pins and apertures and particularly by rigid and non-yielding gear drives and the like. It still was substantially impossible to establish precise initial setting of the clamping rails and with real effectiveness to reset one or both of the clamping rails. It also was difficult to change the tension of the plate, as is needed for different plate materials. It was almost impossible to check this change.

Accordingly, it has been an object of the invention to provide apparatus which simplified the preparatory or auxiliary operation of clamping on of flexible printing plates. It was a further object nevertheless to allow rapid, rational and precise fixing of the printing plates, readjustment of their position and tension, and other related operations, in exactly defined ways and subject to simple and effective correction.

The invention achieves this object with the help of a clamping rail apparatus, the operation of which can start with exact zero positioning of the leading rail. It continues with the use of central clamping means which rapidly provides the required positioning of the follower clamping rail, by a resiliently but precisely acting mechanism. Advantageously this mechanism includes eccentric discs and the like on a central tensioning shaft, such discs being interconnected with the follow clamping rail by lever or wedge means or the like, subject to the action of the spring means between the eccentric disc and the rail, to avoid overloading of the printing plate and to allow automatic tensioning operation. It is preferred to slidably insert a tensioning square between the actuating mechanism and the follower clamping bar and itis additionally preferred to insert compression springs or the like between leading and following clamping rails, to obtain automatic return of these clamping rails into their initial spaced positions.

Use is also made, preferably, of contact markers at the leading edge of the leading clamping rail, and it is still possible to use indexing pin and-slot means for setting the printing plate relative to the leading or following clamping rail, but no longer in ways conducive to the aforementioned difficulties.

DRAWINGS F IG. 1 is a schematic side view of an offset printing machine wherein the invention is used;

FIG. 2 is a similar view, drawn on a larger scale, of a first embodiment of the invention;

FIG. 3 is a similar view of a modification of this first embodiment; I

FIG. 4 is a similar view of another modification.

FIG. 5 is a similar view of a second embodiment of the invention.

FIG. 6 is a fragmentary sectional view of a detail from FIG. 5, seen along lines 6-6 in FIG. 5; and

FIG. 7 is a sectional view taken along lines 7-7 in FIG. 6. I FIG. 8 is a view generally similar to that of FIGS. 25, showing a third embodiment of the invention.

FIG. 9 is a schematic plan view of the indexing system used in conjunction with the invention; and,

FIG. 10 is a section thereof, taken along lines 10-10 in FIG. 9.

THE MACHINE In the machine shown in FIG. 1, sheets to be printed on are supplied in stack holder 29, wherefrom they are brought over feed table 30 into printing unit 31. After engagement with intermediate drums 35, they reach printing cylinder 28. Color roller unit 26 transfers color onto the flexible printing plate 1, tensioned onto plate cylinder 2 (FIG. 2), wherefrom the usual rubber cylinder 27 transfers the color to the sheet on printing cylinder 28 (FIG. 1) Thereafter, transfer drums 33 transfer the sheet to the second printing unit 32, where the same processes are repeated with a different color. Finally the sheet, printed in two colors, reaches outlet section 34, where a new stack of sheets Y is formed from the original sheets x, imprinted-in color.

' As shown in FIG. 2, plate cylinder 2 has a channel 3 formed in its outer part, in form of a recess having approximately segment-shaped cross-section and axial extension, with suitably shaped and rounded edge walls 3-A, 3B, one at each end of the segment. Leading and following clamping rails, 4 ands, are disposed in this channel. Each rail extends in the direction of the channel, parallel to the axis of cylinder 2, and can be shifted at right angles to this direction. This is done under the guidance of transverse tracks or the like, not specially shown, so that mainly the follower rail 4 can move a suitable distance (generally slight) in a direction approximating that of the periphery of the cylin der. The leading and following clamping rails have the corresponding edges of flexible printing plate 1 clamped into suitable slots 8-A of the rails, by clamping means known to the art and not'detailed herein.

As shown in FIGS. 9 and 10, front edge l9 of plate 1 is disposed in slot 8A and is in contact with stop markers 20 suitably disposed in this slot. For accurate and readily correctable setting of plate 1, relative to the print starting line 39 determined by other parts of the printing machine, clamping rail 8 can be adjusted, longitudinally of the printing direction, by adjustment screw 9. As shown in FIG. 2, screw 9 bears'against channel wall 36 and is turned until the leading edge of plate 1 coincides with zero position 00, this edge being fixed by the exposed surface 18 of front contact marker 20.

When this positioning of the front edge has been established, trailing edge 24 of the plate is similarly clamped into follower clamping rail 4 while the two clamping rails are widely spread apart by compression spring 17 and the flexible plate accordingly is not yet tensioned.

According to the invention, tensioning of the plate is then effected by linkage including spring 12 to shift rail 4 against the force of spring 17. As shown in FIG. 2, this linkage includes central tensioning shaft 5 with eccentric cam disc 6 thereon, the shape and position of the cam disc being preferably such that at the inception of tensioning path m there occurs rapid rise of the cam curve, while this curve has lesser rise at the end of this path.

The motion of eccentric disc 6, transmitted by spring 12, displaces lever 7, the other end of which contacts adjustment screw 37 in follower rail 4. It will be seen that compression springs 17 press follower rail 4 against lever 7, just as they press leading rail 8 against leading wall 3--B. These compression springs 17 would tend to leave the printing plate in loose condition on the cylinder, but their force is overcome by the combined action of eccenter 5, spring 12 and lever 7. Interposition of spring 12 has the effect that the tensioning motion effected by the non-yielding linkage 6, 7 will not occur at an excessively rapid rate which could damage the printing plate. In effect, automatic posttensioning of the printing plate, along post-tensioning path n, occurs by virtue of the use of this spring. Evidently the action of the spring can also be adjusted by well known adjustment screw means or the like, not shown.

Referring now to FIG. 3: The plate cylinder and eccenter disc unit can also be constructed with a force transmitting lever 7-A having a shorter load arm and correspondingly greater force in overcoming the reaction of the spring 17, said arm being shown as engaging one end of a tensioning angle 13. This angle may move, parallel to the plane of the drawing, between guiding rails, not shown.

A somewhat similar tensioning angle Iii-A is also utilized in the more extensively modified embodiment of FIG. 4, wherein plate cylinder 2--A has an eccenter 6-A, acting on this angle by a toggle linkage 16 under the control of a spring 15, which in turn is adjusted by a setting device 14, for example an eccentric shaft or disc. In principle, the operation performed in this modification or in that of FIG. 3' is the same as in FIG. 2.

Referring to the embodiment of FIGS. 5, 6 and 7: A cam rod extends in a direction parallel to plate cylinder 2 and is movable in the same direction by the drive shown in FIG. 7, to move the clamping rails by the transmission shown in FIG. 6. As shown in FIG. 7, tensioning angle 13b has rolls 11 mounted thereonwhich can be engaged by wedge-shaped recesses of cam rod 10. When the cam rod is moved in axial direction as shown by the arrow, rolls 11 are pushed out of place to slide tensioning angle 13. Reverse motion of this angle is caused by reverse motion of the cam rod.

The drive of the cam rod, shown in FIG. 7, includes a coarse screw thread in sidewall 44 of channel 3, with a coarse thread nut 41 engaged therein. Interiorly, this nut has fine thread, engaged in turn by fine thread nut 42. The latter nut is rotatably secured to drive shaft 40 which in turn is secured to one end of cam rod 10. The other end of shaft 40 carries a tensioning spring 43 which has the same function as springs 12 and 15 described above. To initiate tensioning, a key 45 is inserted in eccentric apertures of nuts 41, 42 and both nuts are turned thereby, compressing spring 43 and shifting the cam rod, until plate 1 evenly contacts plate cylinder 2. Thereafter, key 45 is withdrawn a short distance and the remaining tensioning path n is traversed by turning only fine thread nut 42.

Still another modification of the invention is shown in FIG. 8, wherein plate cylinder 2C has a central shaft 5 which carries a pair of tines 6-B, 6-C, one for shifting the leading clamping rail by lever 7B and the other for shifting the following clamping 4 by lever 7C. Tensioning springs 12 are interposed in both cases.

It will be understood that tensioning linkage similar to that of FIG. 8 can also be used in the embodiments of FIGS. 3, 4 and 5, in ways which will be obvious to persons skilled in the art. In addition it will be understood that the basic indexing systems of FIGS. 9 and 10, or variants thereof as known to persons skilled in the art, can be used in conjunction with any of the various forms of this invention. In general it is preferred to use the system of FIGS. 8 9 and 10, with contact marks 20 and laterial indexing by pins 22, 25, as in this case all mounting and copying can be done in a way known by itself, with existing equipment of printing plants.

What is claimed is:

l. A rotary printing machine comprising a plate cylinder and means for supporting a printing plate thereon, said cylinder having an axially extending recess formed in its surface, a leading clamping rail for receiving and holding the leading edge of a printing plate, a following clamping rail for receiving and holding the following edge of a printing plate, said rails being disposed axially within said recess and being movable towards and away from each other, a cam rod disposed within the cylinder and movable in a direction parallel to said rails, means moving said rod, a cam follower engaging said cam rod and shiftable by the cam rod in a direction normal to the clamping rails, said cam follower having driving engagement with said following rail to move it towards said leading rail as the cam rod is shifted axially of the cylinder, said cam rod being constituted as means tensioning a plate on the plate cylinder.

2. A rotary printing machine as claimed in claim 1 wherein said cam follower comprises a roller fixed to said following rail and engaging said cam rod.

3. A rotary printing machine as claimed in claim 1 including resilient means biasing said clamping rails apart.

4. A printing machine as claimed in claim 3 including resilient means associated with said cam rod and urging the cam rod in a direction corresponding to that moving said following rail towards the leading rail, said latter resilient means being stronger than said resilient means biasing the clamping rails apart.

5. A rotary printing machine as claimed in claim 1 wherein said leading rail is adjustable relative to an axial edge .of said recess and has means for adjusting the leading rail relative to said edge, said rail including stop means for cooperation with an edge of a printing wherein said means moving said cam rod comprises screw threaded elements adjustable in said cylinder.

9. A rotary printingmachine as claimed in claim 8 wherein said screw threaded elements comprises a first coarse screw threaded element disposed in a correspondingly threaded opening in said cylinder and a second fine threaded element disposed in a corresponding opening in said coarsely screw threaded element, said screw threaded elements being connected to said cam rod through an intermediary of a spring. 

1. A rotary printing machine comprising a plate cylinder and means for supporting a printing plate thereon, said cylinder having an axially extending recess formed in its surface, a leading clamping rail for receiving and holding the leading edge of a printing plate, a following clamping rail for receiving and holding the following edge of a printing plate, said rails being disposed axially within said recess and being movable towards and away from each other, a cam rod disposed within the cylinder and movable in a direction parallel to said rails, means moving said rod, a cam follower engaging said cam rod and shiftable by the cam rod in a direction normal to the clamping rails, said cam follower having driving engagement with said following rail to move it towards said leading rail as the cam rod is shifted axially of the cylinder, said cam rod being constituted as means tensioning a plate on the plate cylinder.
 2. A rotary printing machine as claimed in claim 1 wherein said cam follower comprises a roller fixed to said following rail and engaging said cam rod.
 3. A rotary printing machine as claimed in claim 1 including resilient means biasing said clamping rails apart.
 4. A printing machine as claimed in claim 3 including resilient means associated with said cam rod and urging the cam rod in a direction corresponding to that moving said following rail towards the leading rail, said latter resilient means being stronger than said resilient means biasing the clamping rails apart.
 5. A rotary printing machine as claimed in claim 1 wherein said leading rail is adjustable relative to an axial edge of said recess and has means for adjusting the leading rail relative to said edge, said rail including stop means for cooperation with an edge of a printing plate whereby the printing plate is accurately adjustable relative to a print starting line on the cylinder.
 6. A rotary printing machine as claimed in claim 5 wherein said rail includes a pin for accurately centering a printing plate having a cooperating recess therein.
 7. A rotary printing machine as claimed in claim 1 wherein said means moving said cam rod comprises a first coarse adjusting means and a fine adjusting means.
 8. A rotary printing machine as claimed in claim 7 wherein said means moving said cam rod comprises screw threaded elements adjustable in said cylinder.
 9. A rotary printing machine as claimed in claim 8 wherein said screw threaded elements comprises a first coarse screw threaded element disposed in a correspondingly threaded opening in said cylinder and a second fine threaded element disposed in a corresponding opening in said coarsely screw threaded element, said screw threaded elements being connected to said cam rod through an intermediary of a spring. 